Abstract—In this paper, we present an analytical framework to design system parameters for load-balancing multiuser spectrum decision schemes in cognitive radio (CR) networks. Unlike the non-load-balancing methods that multiple secondary users may contend for the same channel, the considered load-balancing schemes can distribute the traffic loads of secondary users to multiple channels. Based on the preemptive resume priority (PRP) M/G/1 queueing theory, a spectrum decision analytical model is proposed to evaluate the effects of multiple interruptions from the primary user during each link connection, the sensing errors (i.e., missed detection and false alarm) of the secondary users, and the heterogeneous channel capacity. With the objective of minimizing the overall system time of the secondary users, we derive the optimal number of candidate channels and the optimal channel selection probability for the sensing-based and the probability-based spectrum decision schemes, respectively. We find that the probability-based scheme can yield a shorter overall system time compared to the sensing-based scheme when the traffic loads of the secondary users is light, whereas the sensing-based scheme performs better in the condition of heavy traffic loads. If the secondary users can intelligently adopt the best spectrum decision scheme according to sensing time and traffic conditions, the overall system time can be improved by 50 % compared to the existing methods. Index Terms—Cognitive radio, spectrum decision, channel selection, overall system time, preemption, queueing theory. I.

Industrial networks based on IEEE 802.15.4 are spreading, even though the joint requirement on predictability and reliability from industrial applications is hard to fulfil in wireless networks, and the data rate of IEEE 802.15.4 is rather low. With the goal of providing real-time guarantees, with increased reliability and throughput, we propose two multichannel network architectures based on IEEE 802.15.4 with predictable medium access, real-time analysis admission control and transport layer retransmissions. We evaluate the architectures in terms of reliability, utilization, delay, complexity, scalability and energy efficiency. The evaluations show that throughput and reliability can be enhanced through redundancy and concurrency in the frequency domain. 1.

Abstract-Carrier sensing mechanism has been adopted in IEEE 802.11 MAC for collision avoidance under single channel based wireless ad hoc networks. However, due to the hardware limitation, the carrier sensing mechanism can not help much in single transceiver and multi-channel scenarios. In this paper, we propose a pipelining multi-channel (π-Mc) MAC protocol for multi-channel ad hoc networks. The core idea of π-Mc is similar to the pipeline technique. Without collecting each channel usage information, π-Mc not only uses overall channel resources for transmission, but also can prevent DATA collisions. The performance of π-Mc is compared with two well-known multichannel MAC protocols and IEEE 802.11 DCF. Simulation results show that π-Mc is able to achieve 2.50 times the throughput of IEEE 802.11 DCF, as well as respectively outperform DCA and MMAC with a factor of up to 1.43 and 1.32 under three available channels.

Abstract — Wireless networks are making their way into new application areas which have traditionally utilized wired networks as the underlying communication medium. The migration to a wireless medium leads to a cut-down in bandwidth. Even though many parallel frequency channels are available, often only a single frequency is used by today’s standard implementations. Furthermore, application areas such as networked industrial control systems are dependent upon hard real-time services being provided by underlying layers. In order to meet this demands, and at the same time increase network bandwidth, we present a deterministic wireless multichannel MAC protocol, called MC-EDF, which can provide real-time guarantees for deadline-seeking traffic. One channel is used for control traffic, while the rest of the channels are used for data traffic. Simulation results indicate that a utilization of the data channels of 90 % is reachable without any missed deadlines.

Abstract—When an IEEE 802.11 ad hoc network achieves a capacity C using a single channel, the targeted capacity using two channels should be 2 · C. We believe that this should be used as the benchmark for capacity comparisons for multichan-nel schemes. However, most of the dual-channel 802.11 protocols proposed in the literature appear to achieve less than 60 % of the 2 · C targeted capacity. In previous work, we proposed a link-directionality-based dual-channel medium-access-control (MAC) protocol (DCP) to boost the network capacities by up to 78 % of our targeted capacities, i.e., 78 % × 2 · C = 1.56 · C. However, the DCP still fails to reach the 2 · C capacity target due to the overheads incurred by the protocol. In this paper, we implement a signal-to-interference ratio (SIR) comparison algorithm (SCA) on top of the DCP in an attempt to further improve network capacity. This algorithm incurs relatively small overheads and can further relax the protocol constraints that are imposed by the virtual carrier-sensing mechanism. Interestingly, while the capacity of the pure DCP decreases when link lengths are short, the capacity of the pure SCA increases when link lengths are short. The two algorithms compensate for the downside of each other to bring about a more uniform capacity improvement. Simulations show that the proposed scheme [described as DCP with SCA (DCPwSCA)] can increase the network throughputs by 430 % in lattice topologies and 213 % in random topologies. Index Terms—Ad hoc network, capacity, IEEE 802.11, medium-access-control (MAC) protocol, multichannel.